> "with rules you don't need everything to be and s-expression"

I am unsure if I would call it a feature.

From a Perl point of view, I think it's the right way to go. There are a few "standard" tricks to simulate extending Perl5, but they often feel hackish. From my understanding this will be more flexible and explicit. I don't have the Lisp experience to compare the two. My guess is Lisp macros will still be more flexible but the gap will be significantly narrowed.